A plain or sliding bearing as opposed to a roller bearing has a surface in sliding friction contact with another surface of a moving member, e.g. a shaft to be journaled.
The bearing of British Pat. No. 524,128 has a surface composed of an anti-friction layer which is divided into a plurality of separate sections by thin ribs of metal which is harder than the material used for the anti-friction layer. The ribs extend essentially in circumferential direction of the sliding surface of the bearing and are arranged evenly throughout the bearing metal e.g. in a helical or screwthread pattern. Such bearings are thus also called grooved or helical sliding bearings.
These bearings have the disadvantage that the ridges of the ribs are exposed which means that the hard material (of aluminum or copper) of which these ribs are made is exposed. This considerably complicates the required adjustment of the bearing to the trunnion during the running-in phase. Moreover, the sliding and emergency running properties of the ribs are insufficient during disturbances caused, e.g., by oil deficiency or accumulation of dirt.
Consequently, it has been proposed to coat the ribs with a thin layer of softer lead alloy or tin alloy. In the case of sliding bearings for large engines, the German patent publication No. DE-OS 19 30 010 proposes to provide the metallic layer applied onto the bearing ridges with crossing indentations and to cover it with a layer of softer material by filling the indentations. Although the loading capacity of sliding bearings increases with decreasing thickness of the sliding surface, the support ribs can still be coated with a relatively thick layer between 0.01 to 0.05 mm thickness. This range can easily be maintained by reboring the sliding surface a second time after electroplating.
Highly loaded connecting rod bearings and main bearings of motor vehicles require in general a total thickness of the sliding surface of approximately 0.01 to 0.03 mm. To counter fatigue, this thickness range may also not be exceeded in sliding surfaces of grooved or helical sliding bearings for such engines. In view of the higher load a considerably lower thickness of the cover layer must be selected than would be the case in large motors. To guarantee this thickness range also during an industrial scale manufacture, it is necessary to limit the tolerances during the cutting of the sliding surface to such an extent that an economic production is unattainable. It has been proposed to apply the covering layer in an additional working cycle, e.g. by electroplating, cathodic sputtering or spraying. However, this is complicated and cumbersome and thus also not economical. Moreover, the provision of such an additional working cycle is not technically feasible in some types of bearing materials.